<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .active{text-decoration:underline;}
        .text-danger{font-weight:blod;}
    </style>
</head>
<body>
    <div id = "app">
        <div v -blind:class="{active:isActive,'text-danger':hasError}">Hello</div>
        <div v-blind:class="classObj">Vue.js</div>
    </div>
    <script>
        var vm=new Vue({
            el:"app",
            data:{
                isActive:true,
                hasError:true,
                classObj:{
                    active:true,
                    'text-danger':true
                }
            }
        })
    </script>
</body>
</html>